The gun buyback in a parking lot in downtown Seattle was scheduled to go from 9 a.m. to 3 p.m., but ended early because of the large crowd. Police say that after two hours, more than 160 guns had been turned in and $35,000 in gift cards had been distributed. Other buybacks are planned for later this year.

Seattle Mayor Mike McGinn and other leaders have praised the buyback effort, saying it will reduce gun violence. But statistics show a previous effort in Seattle failed to do that.

In the six months after Seattle's 1992 gun buyback — the city's only other such effort — the average number of firearms-related homicides increased. The mean number of firearms-related assaults in Seattle also increased, as did the mean number of robberies with guns. Even the mean number of accidental shooting deaths more than doubled, according to data in a government journal.

The city has collected donations totaling nearly $120,000 to pay for a series of gun buyback events.

People will receive up to $100 gift cards for hand guns, shotguns and rifles, and up to $200 for assault weapons. Full gift card value will only be given for working weapons.